This invention relates to a control system for controlling the pressure on chocolate refining machine roll bearings.
As is known, chocolate refining machines require that the pressure exerted on the bearings of the refining rolls downstream of the feeding roll pair be adjustable if the machine is to accommodate chocolate pastes having different percentages of fat. Such fat percentages may vary quite significantly, e.g. within a range up to 4-5%, depending on the chocolate products to be prepared from such pastes.
As is known, by controlling the pressure on the refining roll bearings, the plasticity of the chocolate film delivered can be changed.
Currently in use are two different methods of determining a pressure change on the bearings of refining rolls downstream of the feeding pair.
With a first method, the pressure on each roll pair can be changed such that the refining machine is imparted with maximum flexibility to accommodate chocolate pastes whose fat contents vary within the broadest range. To carry out this kind of adjustment, termed "linked multi-pressure control", a control circuit is provided which comprises, for each refining roll, a double-acting hydraulic-pneumatic pressure step-up device which is connected with its hydraulic side to a hydraulic unit associated with the bearings of one refining roll pair, and with its pneumatic side, and through a branch line containing a respective pressure regulator, to a common riser associated with a compressed air source. By operating a pressure regulator, a pressure change is brought about on the bearings of the roll pair served by the respective circuit branch, while the pressure on the bearings of the other refining rolls is kept unaltered. Refining machines equipped with this control system are, accordingly, adapted for processing different chocolate paste types, i.e. for ultimate chocolate products of different types.
With the second method of controlling the refining roll pressure, which consists of acting simultaneously on all the bearings of the refining rolls downstream of the feeding roll pair, the pressure is applied to the bearings of the delivery roll and is transferred by metal-to-metal continuity to the refining rolls downstream of the feeding roll pair. With the latter method, called "linked single-pressure control", pressure can be adjusted in a simpler way than with the "linked multi-pressure control", but such refining machines cannot accept chocolate pastes for refinement which are uneven as regards their fat contents and plasticities.
Thus, currently available are refining machines featuring a more flexible operation, i.e. adapted for processing a range of chocolate pastes, and a more sophisticated and critical adjustment of the refining roll pressures, as well as refining machines which are easier and simpler to adjust but can only accept alike chocolate pastes.
This situation is apt to make the choice of the type of control, or refining machine to be purchased, by the potential user a difficult one.